diff --git a/content/treestyletab/treestyletab.js b/content/treestyletab/treestyletab.js
index 62acee0b..bbc599ad 100644
--- a/content/treestyletab/treestyletab.js
+++ b/content/treestyletab/treestyletab.js
@@ -108,6 +108,30 @@ var TreeStyleTabService = {
 	{
 		return window.gToolbox && gToolbox.customizing;
 	},
+ 
+	maxTabbarWidth : function TSTService_maxTabbarWidth(aWidth, aTabBrowser) 
+	{
+		aTabBrowser = aTabBrowser || this.browser;
+		return Math.min(
+				aWidth,
+				parseInt(Math.min(
+					window.innerWidth,
+					aTabBrowser.boxObject.width
+				) * 0.9)
+			);
+	},
+ 
+	maxTabbarHeight : function TSTService_maxTabbarHeight(aHeight, aTabBrowser) 
+	{
+		aTabBrowser = aTabBrowser || this.browser;
+		return Math.min(
+				aHeight,
+				parseInt(Math.min(
+					window.innerHeight,
+					aTabBrowser.boxObject.height
+				) * 0.9)
+			);
+	},
   
 /* Initializing */ 
 	
@@ -1443,13 +1467,13 @@ catch(e) {
 		window.setTimeout(function(aSelf) {
 			if (!b.treeStyleTab.clickedOnTabbarResizerGrippy) {
 				if (!b.treeStyleTab.isVertical) {
-					aSelf.setTreePref('tabbar.height', box.height);
+					aSelf.setTreePref('tabbar.height', aSelf.maxTabbarHeight(box.height, b));
 				}
 				else {
 					if (!b.treeStyleTab.autoHide.expanded)
-						aSelf.setTreePref('tabbar.shrunkenWidth', box.width);
+						aSelf.setTreePref('tabbar.shrunkenWidth', aSelf.maxTabbarWidth(box.width, b));
 					else
-						aSelf.setTreePref('tabbar.width', box.width);
+						aSelf.setTreePref('tabbar.width', aSelf.maxTabbarWidth(box.width, b));
 				}
 			}
 			b.treeStyleTab.updateFloatingTabbar();
@@ -1559,7 +1583,7 @@ catch(e) {
 		}, 250, this);
 	},
 	updateAeroPeekPreviewsTimer : null,
-	updateAeroPeekPreviewsInternal : function TSTService_updateAeroPeekPreviewsInternal() 
+	updateAeroPeekPreviewsInternal : function TSTService_updateAeroPeekPreviewsInternal()
 	{
 		this.AeroPeek.windows.some(function(aTabWindow) {
 			if (aTabWindow.win == window) {
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index 9c7bcabf..d686cf25 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -942,7 +942,8 @@ TreeStyleTabBrowser.prototype = {
 
 			this.setTabbrowserAttribute(this.kMODE, 'vertical');
 
-			this.setTabStripAttribute('width', this.getTreePref('tabbar.width'));
+			let width = this.maxTabbarWidth(this.getTreePref('tabbar.width'), b);
+			this.setTabStripAttribute('width', width);
 			this.removeTabStripAttribute('height');
 			b.mPanelContainer.removeAttribute('height');
 
@@ -960,7 +961,7 @@ TreeStyleTabBrowser.prototype = {
 					/* in Firefox 3, the width of the rightside tab bar
 					   unexpectedly becomes 0 on the startup. so, we have
 					   to set the width again. */
-					aSelf.setTabStripAttribute('width', aSelf.getTreePref('tabbar.width'));
+					aSelf.setTabStripAttribute('width', width);
 					indicator.setAttribute('ordinal', 1);
 					aSelf.setTabStripAttribute('ordinal', 30);
 					aSplitter.setAttribute('ordinal', 20);
@@ -1149,7 +1150,7 @@ TreeStyleTabBrowser.prototype = {
 			}
 			else {
 				this.removeTabbrowserAttribute(this.kFIXED, b);
-				this.setTabStripAttribute('height', this.getTreePref('tabbar.height'));
+				this.setTabStripAttribute('height', this.maxTabbarHeight(this.getTreePref('tabbar.height'), b));
 				if (toggleTabsOnTop)
 					toggleTabsOnTop.setAttribute('disabled', true);
 			}
diff --git a/content/treestyletab/treestyletabbrowser_autoHide.js b/content/treestyletab/treestyletabbrowser_autoHide.js
index 1dc1f18e..649038b0 100644
--- a/content/treestyletab/treestyletabbrowser_autoHide.js
+++ b/content/treestyletab/treestyletabbrowser_autoHide.js
@@ -370,9 +370,9 @@ TreeStyleTabBrowserAutoHide.prototype = {
 		if (aForceExpanded ||
 			this.expanded ||
 			this.mode !=  this.kMODE_SHRINK)
-			this.setTreePref('tabbar.width', aWidth);
+			this.setTreePref('tabbar.width', this.mOwner.maxTabbarWidth(aWidth));
 		else
-			this.setTreePref('tabbar.shrunkenWidth', aWidth);
+			this.setTreePref('tabbar.shrunkenWidth', this.mOwner.maxTabbarWidth(aWidth));
 	},
  
 	updateMenuItem : function TSTAutoHide_updateMenuItem(aNode) 
@@ -513,7 +513,7 @@ TreeStyleTabBrowserAutoHide.prototype = {
 			default:
 			case this.kMODE_SHRINK:
 				if (pos == 'left' || pos == 'right')
-					sv.setTabStripAttribute('width', this.getTreePref('tabbar.width'));
+					sv.setTabStripAttribute('width', sv.maxTabbarWidth(this.getTreePref('tabbar.width')));
 				break;
 		}
 		sv.updateFloatingTabbar(true);